The present invention relates to a method of mixing steel fiber reinforced concrete, and more particularly the invention relates to a method of introducing steel fibers into components of concrete or into an uncured concrete made up of these components.
The most important matter that must be considered in mixing the components of steel fiber reinforced concrete is how to uniformly distribute steel fibers into steel fiber reinforced concrete. This becomes increasingly important in case the amount of steel fibers is increased so as to increase the concrete strength. In the mixing of steel fiber reinforced concrete, the steel fibers tend to interlock with one another and conglomerate to form into balls. Such ball-shaped conglomerates will be made up of steel fibers only, steel fibers and paste, steel fibers and aggregates, steel fibers and mortar, etc., and it is difficult to break up such conglomerates into pieces once the conglomerates have been formed. The formation of such ball-shaped conglomerates will reduce the strength of steel fiber reinforced concrete considerably. As a result, to eliminate the formation of such conglomerates is the most important requirement which must be met during the mixing of steel fiber reinforced concrete.
Generally, steel fibers are packed and transported in box containers, e.g., corrugated boxes, and consequently the steel fibers interlock with one another thus gathering into conglomerate-like masses by the time that the steel fibers arrive at the job site where they are used. To uniformly scatter and distribute steel fibers, they are charged into a mixer after manually unraveling when the amount of steel fibers used is small, and where a large amount of steel fibers are used they are charged into a mixer after they have been placed in a machine, such as a dispenser or vibrating screen. While this has the effect of practically preventing the formation of conglomerates during mixing, from the standpoint of mass production and product quality there is a disadvantage that the manual as well as mechanical unraveling operation requires a long period of time. To overcome this difficulty, it is necessary to provide an unpacking and unraveling equipment of a sufficient capacity corresponding to the capacity of a concrete mixing plant. For example, in the case of a batcher plant including a forced agitation mixer of 3000 Lit. capacity, it is necessary to use about 3 dispensers each having a capacity of 60 Kg/min, and the manpower for unpacking and charging purposes must meet the requirements of the three dispensers.